Replace objects with a group of objects using Python
If you create an empty, and set it to represent an instance of the brokenCube group (Properties panel -> Object -> Duplication -> Group), you can then simply add that empty, to add all the objects in the group.

Demo: break_demo.blend

PS: Cell fracture seems to create areas with a very large number of very small parts. I would recommend that you remove most of them (as I did in the demo), if you want to have good performance.